Using Potentiometric Electrodes Based on Nonselective Polymeric Membranes as Potential Universal Detectors for Ion Chromatography: Investigating an Original Research Problem from an Inquiry-Based-Learning Perspective

Because traditional laboratory practices in advanced chemistry education are being replaced by inquiry based approaches, we present herein a new laboratory activity based on a small research project that was designed and executed by students. The laboratory project aims at answering a well-defined research question: how far can potentiometric electrodes based on nonselective polymeric membranes be used as universal detectors in ion chromatography (IC)? Hence, the experiments were designed and conducted to explore the analytical performances of potentiometric electrodes based on different commercial membranes that are typically used in electrodialysis. The nonselective behavior shown by the electrodes permits a critical evaluation of their further implementation as a universal detector of anions in regular IC. Thus, the students were able to integrate a nonselective potentiometric sensor to analyze several anions in flow mode, mimicking the signal that is to be obtained using such electrodes as an IC detector. The proposed practice covers different pedagogical purposes: (i) to develop competence toward thinking like a scientist through reflective teaching; (ii) to promote argumentation skills and critical decision making; (iii) to improve students' research-planning and experimental-design skills; (iv) to refresh conceptual knowledge about analytical detectors, which typically goes unnoticed in laboratory practices; and (v) to reinforce students' knowledge about the basis of potentiometry. Furthermore, the present document may serve as an easy guide to develop other laboratory practices based on potentiometric sensors.